1. Field of the Invention
The present invention relates to a bicycle wheel rim, more particularly to a bicycle wheel rim with an enhanced braking effect.
2. Description of the Related Art
U.S. Pat. No. 3,433,327 discloses a bicycle wheel rim 1 which, as shown in FIG. 1, has an external braking surface that is formed with a series of parallel grooves 11 in an undulating pattern and a plurality of transverse grooves 13 that extend in radial directions to interconnect the undulating parallel grooves 11. When it rains, or when the bicycle is ridden through puddles of water, the water collected in the parallel grooves 11 can escape laterally via the transverse grooves 13 and travel away from the center of the braking surface so as to pass beyond the area to which a brake pad is applied. However, as the transverse grooves 13 do not open at a radial inner edge portion 14 of the braking surface, and at a radial outer edge portion 15 of the same, water can still accumulate in the undulating parallel grooves 11 and the transverse grooves 13 to form a fluid film that lubricates the braking surface, especially when the bicycle is ridden under heavy rain conditions.